Remember: a square is a rectangle but a rectangle is not always a square. Similarly, a dietitian is a nutritionist but a nutritionist is not always a dietitian. A registered dietitian is the only clinically trained and licensed nutrition professional recognized nationally. They complete at least 4 years of school, 1200 internship hours, a national credentialing exam, and maintain continuing nutrition education. In contrast, there are no national qualifications to become a nutritionist. States have varying licensing and regulation requirements, while some states have no requirements. We choose registered dietitians to ensure the most credible nutrition guidance is available to you.